Luke Coletti <[EMAIL PROTECTED]> writes: > Below are some data that may help you, the calculation date is > Jan 1 Noon UT, EoT values are in the form TA-TM. The discussion to date > has been more about the variation of our orbit and Earth's alignment > within, however all these events need to be related to a calendar and > since there is not a even multiple of days in our orbital period I think > you can see how the EoT becomes unsynced. Note that after twenty years, > which falls on a four year boundary from the start, the delta is 1.3 > secs. > ... > Column 1: day of year, Column 2: year, Column 3: days in year > Column 4: days from J2000, Column 5: Solar Day Length, secs > Column 6: EoT, secs, Column 7: EoT delta, secs > > 1 2000 366 +0.0 -28.5750 -198.0059 +0.000000 > 1 2001 365 +366.0 -28.3493 -219.3062 -21.300274 > 1 2002 365 +731.0 -28.4230 -212.3139 -14.307972 > 1 2003 365 +1096.0 -28.4950 -205.3031 -7.297152 > 1 2004 366 +1461.0 -28.5650 -198.2742 -0.268264 > 1 2005 365 +1827.0 -28.3388 -219.5665 -21.560536 > ...
We see a -28.3 sec jump when the calendar is changed by one day. What's left over is -0.268 seconds, which accumulates. It would seem that the difference would reach -28.3 sec after 422 years, at which time we would want to leap over a leap year. Why does the Gregorian calendar skip a leap year every 133 years (on average)? Whatever the ratio between the length of the day and the length of the year, one can find calendrical rules which approximate the ratio. Over what time scale do irregularities in the perturbations of the planets or slowing down of the Earth's rotation rate through tidal drag cange the ratio enough to make simple leap year type rules invalid? Art Carlson
